Telephone circuit and apparatus



(No Model.) 2 Sheet s- She'et 1.

J. A. BARRETT. I

TELEPHONE CIRCUIT AND APPARATUS.

No. 397,331. Patented Feb. 5,1889.

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(No Model.) V

2 Sl1eetsSheei:v 2.

J. A. BARRETT.

- TELEPHONE CIRCUIT AND APPARATUS.

Patented Feb. 5. 1889.

N rnn STATES PATENT GrrIcE,

JOHN A. BARRETT, OF BROOKLYN, NEWV YORK, ASSIGNOR TO THE vAMERI- CANTELEPHONE AND TELEGRAPH COMPANY, OF NEYV YORK.

TELEPHONE CIRCUIT AND APPARATUS.

SPECIFICATION forming part of Letters Patent N 0. 397,331, datedFebruary 5, 1889.

Application filed May 9, 1888- $erial No. 273,304. (No model.)

To all whom it may concern.-

Be it known that I, JOHN A. BARRETT, residing at Brooklyn, in the countyof Kings and State of New York, have invented certain Improvements inTelephone Circuits and Apparatus, of which the following is aspecification.

The object of my invention is to reduce,

the original changes, the proximity of the con-- ductors in question,and the amount of surface exposed to inductive action. Such inducedvariations are very troublesome in their effect upon telephonicinstruments included in the circuit of either conductor, and toneutralize the ill effects thereof in the telephonecircuit, and, infact, to neutralize foreign currents therein, whether proceeding fromparallel lines or from other causes, resort has been had to a completemetallic or double wire circuit in which both wires being parallel toone another and substantially equidistant from the source of disturbancethe adverse currents meet and neutralize one another. Such substantialequidistance is, 110wever, a condition of absolute success in theachievement of the desired end, and the degree of success is in allcases proportionate to the degree of exactness attained in establishingequidistance between each of the two conductors of a circuit and theseveral sources of disturbance. It is-possible to perfect such anarrangement only when the two wires of each circuit are or can betwisted round one another, and this practice, though generally feasiblein cables, is not easily carried out in pole-lines, for obvious reasons.

It has been found that when a number of metallic circuits are supportedupon poles in the air in parallelism with one another the immunity ofthe several circuits from inductive disturbance is not perfect, and thisimperfection in operation arises partly from the circumstance that thetwo conductors of any line are not, as ordinarily arranged, equidistantfrom the other circuits, and partly from another cause, to which I.shall. hereinafter advert.

To obtain the requisite conditions as far as possible, I cross-connectthe two wires of each metallic circuit at the several cable-boxes atriver-crossings and at as many other points upon the line as maybe foundconvenient. In some cases it may be found necessary to so alternate thepoints of support upon the successive poles that the two wires of eachcircuit shall be actually twisted round one another many times betweenthe respective termini of the line, so that each conductor of each lineis in turn subjected to the same inductive influence as the other, andneutralization of adverse currents is thus in a great measure effected.

Actual practice hasalso demonstrated that even when the lines weresubstantially balanced in the manner described above one of the twolines of a circuit was more susceptible than the other to inductivedisturb- 7 5 ance, and I have further ascertained that this phenomenonwas and is due to the circumstance that the apparent balance existingbetween the two sides of the circuit is, in fact, quite imperfect, andthat the said imperfection arises from the presence of thereceivingmagneto-telephone helix on one side or the other of thesecondary helix of the transmitter, which, included directly in theline-circuit, may be regarded in each case as the source of transmittingenergy for the circuit.

The electrical currents transmitted in any circuit act moreenergetically on that side of the circuit which does not include thereceiving-telephone helix, and are made slug- 9o gish or are retardedupon that side in which the said helix is included; hence the currentsin the two conductors of any single circuit, being uneven in strengthand character, exercise different degrees of inductive influ- 5 enceupon the surrounding or neighboring circuits, and the two sides of suchcircuits are in turn also dilferentially susceptible to the saidinfluence when emanating from other cir cuits.

To counteract these disturbing influences, and in general furtherance ofthe object of my invention, as hereinbefore stated, the inventionconsists in so disposing the magnetohelix with respect to the source ofundulatory energy that the balance of the two sides of the circuit willnot be thereby disturbed, and in combining this improvement with. thesew eral cross-connections of the two conductors of the circuit, so thatboth expedients will co-operate for the maintenance of said balance.

In the drawings which illustrate and which are a part of thisspecification, Figure 1 shows a system of parallel telephone-linescomprising both metallic and ground return-0ircuits. Fig. 2 representsin diagram a single metallic telephone-circuit cross connected at anumber of points between its termini. Fig. 3 is a diagram of a metalliccross-connected eircuit, showing the balanced position of the relceiver. Fig. l is a diagram illustrating a modification in the plan ofconnecting the receiver with respect to the transmitter secondary coil,and Figs. 5 and 6 are inductioncoils constructed .in accordance with myinvention.

In Fig. l, 1,2,and 3 are metallic and ground return paralleltelephone-circuits extending between two stations, X and Z, at whichstations they are provided, in the usual manner, with a telephone, 2.The diagram indicates the order in which any number of circuits may besupported on, the poles or cross-arms, and it is obvious that any one ora number of circuits so arranged cannot exercise an equal inductiveeffect upon both direct and return wire of any one circuit, inasmuch as,unless special measures are adopted, although the two wires are parallelto one another, they are not equidistant from each of the othercircuits. Thus the ground-eircuit I would exercise a stronger influenceover wire a of circuit 2 than it could over wire I) of the same circuit.

Fig. 2 shows the first step in my improvement, and also illustrates theessentiality of the second.

A double-wire circuit, I, is shown extending between two stations, A andB, and it is to be assumed that many or a number of like circuits areextended parallel thereto upon the same main supports. Each station isprovided with the usual telephonic apparatus comprising a receiver and atransmitter. The transmitter T is included in the ordinary way incircuit with a local battery, l3,and the primary helix 1 of aninduction-coil, the secondary helix 6 whereof is included inthelinecircuit, and is consequently, so far as the said. line-circuitconcerned, the actual source of the electrical energy by means of:whichvocal transmission is effected.

The receiver t is also in the main circuit.

The two wires 3 and 4: of the circuit are Each cablehouse upon the lineof route will preferably be utilized, and the wires may also besubjected to a series of gradual transpositions upon the poles, so thatbetween the termini of the line each is brought into the inductive lineof the other a number of times, and the neutralization of adversecurrents is in a con.- siderable degree cliected.

The appliances at both stations are practically alike. It is tobe noted,considering the iiuluction-coil (i as the source of energy for thecircuit, that the receiving-telephone is connected in the said circuiton one side thereof. The helix of the said telephone is not only woundto a considerable resistance, but also encircles a magnetic core. Itspresence, therefore, disturbs the balance which would otherwise existbetween the two sides of the circuit, and, ashereinbefore explained, theresults are disadvantageous, whether the circuit as a whole be regardedas the transmitter or recipient of the induccal and distnrbing currents.I have therefore (IGXISOJI and adopted the expedient shown in Fig. 3, inwhich the receiving-telepllone t is connected in. the middle of thesecondary helix, the wire thereof being for that purpose divided intotwo equal portions, 8, the two inner ends of which are brought out andconnected with the receiver-terminals through suitable connections, E).lVhen so arranged, it is evident not only that the tr:msmitter-coil hasan electro-motive force fully as potent as if it were uiulividcd, but that the electro-motive l'orce developed therein operates with equal vigoron both conductors 3 and 4 of the circuit, which are thus balanced. Theconductorsbalanced in this way are, as hereinbei'ore indicated, lessreceptive to currents induced by other lines, and have also lessinfluence upon other lines, and when all the parallel lines of acompletesystem are so arranged the results are extremely beneficial upon thegeneral. operation of the series.

An induction-miil constructeil as in Fig. :3 may be employed for theabove purpose. (J is a baseboard upon which the induetorium. may bemounted. The inner or primary coil, is connected with terminalbinding-screws 13, and the outer secondary or line coil terminated atthe outer ends thereof by the binding-screws ll, the severed centralends being attached to the binding-screws S, to which the terminals ofthe rcceivi ng-tcleph on e f are like wise connected.

In Fig. l I show a modified plan of divid ing the resistance of thetelephone lnlix between the two sides of the circuit, which modificationis especially applicable to apparatus already in use, and which. istherefore not readily accessible or convenient for radical. change. Bythis plan the two line-com ductors 3 and l are connected with the twoterminals 11 of the secondary helix 1() of an induction-coil in theordinary way, and the telephonc conductors are likewise united to thesame terminals. The telephone-helix united by its double conducting-corda to these binding-screws, constituting a derived circuit or shunt roundthe resistance of the induction-coil helix.

Fig. 6 shows another form in which the inductorium used in accordancewith" the first plan may bemadc. Two sn'iall but completeinduction-coils may be provided, as D D. These are shown as beingmounted upon the same base 0. The two primary helices are united by awire joinin g their inner terminals 12, while their outer terminals 14:are connected in the transmitter-oircuit. The secondary helices areconnected by means of their outer terminals 13 in the main-line circuit,while the two inner terminals 15 are eon nected with thereceiving-telephone t.

I do not herein claim as my invention the plan of diminishing theinduced currents which disturb telephone-circuits by cross connectingthe two wires of the said circuits; but

I do claim- 1. The combination, with a telephonic circuit, of atransmitter having the secondary or line circuit of its induction-coildivided into two substantially equal parts, and a receiving-telephoneconnected to line between the parts of said coil, as set forth.

2. The combination, with a telephonic circuit, of atelephone-transmitter, an inductioncoil, whereby the electrical changesproduced by the action of said transmitter are propagated through saidcircuit, and a telephonereceiver connected in approximately the middleof the secondary or line helix of said induction-coil, said helix beingthe source of electrical energy for said circuit, substantially asdescribed.

3. The combination, with a telephonic circuit, of atelephone-transmitter, an inductioncoil therefor, havingits secondary orline helix, which constitutes the source of energy in said circuit,divided at or about its center of resistance, and a receiving-telcphonelooped or connected to the severed terminals, substantially asdescribed.

'- at. The combination of a metallic or double conductortelephonecircuit having its two sides crossconnected or transposed atone or more points with a transmitterinduction-coil having its secondaryhelix included in the said circuit and divided at its center, and areceiving-telephone interposed between the two halves of the said coil,substantially equalized and a balance between them maintained.

In testimony whereof I h aye sign ed my name to this specification, inthe presence of two subscribing witnesses, this 22d day of August, 1887.

JOHN A. BARRETT.

lVitnesses:

F. DELYsLE SMITH, THos. I), LocKWoon.

